Distributed generators are becoming increasingly common components of electrical grids. They typically use renewable power generating components such as photovoltaic (PV) solar panels or wind turbines but can also use non-renewable power sources such as natural gas. Distributed generators may be widely distributed across the electrical grid and connected to either the low or medium voltage portions of the electrical grid. These distributed generators inject synchronized current into the electrical grid.
A number of PV panels arranged in an array may be connected to the electrical grid through a central inverter. However, central inverters are associated with one or more drawbacks. One drawback of a central inverter is the lowering of the overall efficiency of the PV panel array as all PV panels in a string of panels must operate at the same current. An alternative to using a central inverter is to provide an inverter to each PV panel. This allows each panel to operate at its maximum power point regardless of the performance of other PV panels in the array.
Inverters for individual PV panels may have their functionality distributed across multiple components. For example, inverter components for converting the Direct Current (DC) output of the PV panel to Alternating Current (AC) suitable for injecting into the electrical grid may be physically located at the PV panel. A gateway component may include additional functionality for monitoring and controlling the inverters and may be located remotely from the panel. The partitioning of the inverter functionality in this manner allows for common functionality of the inverters to be collected at a single point in the gateway, thereby possibly reducing the complexity of the individual inverter components located at the panels. Further, the partitioning of the inverter functionality may allow simplified upgrading of certain functionality located in the gateway throughout the life of the PV panels. While partitioning the functionality of the inverters may provide benefits, the inverters still function as individual inverters, increasing the complexity of controlling the PV panels.
Inverters, and in particular inverters for PV panels, may not include grid stability functionality more common for inverters connected to larger power sources. The grid stability functionality may include, for example, fault ride through, demand response, reduction of active power with over voltage/frequency or injection of reactive power. When the individual inverters of PV panels detect grid instability, that is the operating parameters of the grid falls outside of particular thresholds, the inverters may simply disconnect from the grid. Such an approach is suitable if the inverters are supplying a small amount of power to the grid; however, as distributed generation becomes more common, the amount of power supplied to the grid increases. In such cases, an inverter disconnecting from the grid individually may not pose a problem; however, if all the inverters disconnect at the same time the resultant decrease in power supplied to the grid may lead to further grid instability.
Although there are advantages with the use of distributed power generation in an electrical grid, as the amount of power provided by these distributed generators increases, the need for more advanced control of the individual power generators arises.